Magnet having regions of different magnetic properties and method for forming such a magnet

ABSTRACT

This application concerns a magnet having a magnet body as well as a method for manufacturing such a magnet. The magnet body has a first region with first magnetic properties and a second region with second magnetic properties that are different to the first properties. Owing to the manufacturing process of the magnet body, the relative location of the first region and the second region within the magnet body is freely predeterminable.

TECHNICAL FIELD

The present invention relates mainly to a magnet and to a method forforming such a magnet. Hereinafter, the term ‘magnet’ is understood asan object that is able to produce a magnetic field.

BACKGROUND ART

Magnetic materials for energy applications are usually divided into twomain groups: hard magnets (often referred to as permanent magnets) andsoft magnets.

Hard magnets typically have coercivity values Hc>10-100 kA/m, whereasfor soft magnets typically the coercivity is Hc<1 kA/m. In between thesegroups the semi-hard magnetic materials include all alloys whosecoercivity (Hc) is between that of soft magnetic and hard magneticmaterials.

Permanent magnets (hereinafter abbreviated as “PM”) are typically usedin electrical machines (motors, generators). The most advanced permanentmagnets today are based on rare earth (RE) metals. The term “rare earth”is commonly abbreviated as “RE”. RE is one of the elements of theLanthanide series in the periodic table of elements. Said Lanthanideseries comprise the chemical elements Lanthanum (La), Cerium (Ce),Praseodymium (Pr), Neodymium (Nd), Promethium (Pm), Samarium (Sm),Europium (Eu), Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium(Ho), Erbium (Er), Thulium (Tm), Ytterbium (Yb), Lutetium (Lu).

RE based magnets are especially important, as they allow machine designswith high performance, high energy efficiency, and overall compactnessin dimension. Typical rare earth-based permanent magnets materials areintermetallic alloys based on Nd—Fe—B, (Nd—Dy)—Fe—B, and Sm—Co. A rangeof additional chemical elements can be present in the magnet bodies inorder to optimize specific properties and also the ratios of the baseelements can vary within one type of magnets.

Sintered, dense rare earth-based permanent magnets materials exhibit thehighest magnetic performance, i.e. the highest coercivity Hc and thehighest remanence B_(r). A drawback of the rare earth-based permanentmagnets materials resides in that they resides in that the rare earthelements used are that expensive that their share forms an essentialportion of the total cost for manufacturing the magnet body. Thatdisadvantage holds particularly true for those magnet bodies containingheavy rare earth elements (hereinafter referred to as HRE elements). HREelements are Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er),Thulium (Tm), Ytterbium (Yb) and Lutetium (Lu).

The high total cost depends not only on the high raw material costs ofthe rare earth metals, but also on the very complex processing route.Because of the high reactivity of RE metals with oxygen, all processingsteps have to be performed under protective atmospheres in order toavoid detrimental impact on the magnetic properties. In order to achievea maximum magnetic performance, particles can be oriented by applying ahigh magnetic field before and during the pressing step. Suchmanufactured magnets are usually higher in performance compared tonon-oriented grades. All known powder metallurgy processing routes forRE-based permanent magnets are limited to the manufacture of very simplegeometries, because the shaping is based on simple uniaxialdie-pressing, isostatic pressing, or hot deformation in a uniaxialdie-pressing step. Already very simple geometrical features, like aslightly curved surface instead of a flat surface, comes with asignificant higher price of the magnet, because expensive additionalmachining steps (grinding of the hard materials) have to be employed.This limitation to simple geometries is a big limitation and drawbackfor the design of advanced, more energy efficient machines, which wouldprofit form more complex shaped magnets.

Yet another important property of PM materials for electrical machineapplications is there maximum operating temperature. RE based PMmaterials suffer from demagnetization at elevated temperatures. In theNd—Fe—B system partial substitution of Nd with heavy rare earth elements(typ. 4 to 6 at. % Dy) can extend the operating temperature fromtypically 100° C. (for normal Nd—Fe—B) to about 150 to 200° C. (for Dydoped Nd—Fe—B). In advanced machine designs with increased powerdensities this extended operating temperature are commonly desired.However, the improved temperature stability comes with a high cost. Dueto the exceptionally high cost of heavy RE metals, the cost of such Dydoped or other heavy RE doped magnets is significantly higher comparedto conventional RE based PM.

A further problem of RE based PM materials is their intrinsically highsusceptibility for corrosion. To enable long-term application, alloyingelements for improved corrosion behavior or protective coatings have tobe applied.

One way of overcoming this drawback resides in arranging the expensiveHRE elements selectively in those areas of the magnet body whereenhanced magnetic characteristics are actually required andindispensable once built in an electric device, while keeping the restof the magnet essentially free of HRE.

One approach of lowering the overall costs of a magnet by selectiveprovision of RE elements resides in diffusing Dysprosium (Dy) along thegrain boundaries of the magnet body. The magnet body consisting of aNeodymium-Iron Boron alloy (NdFeB) is sintered first by common methodsknown in the art. After forming the magnet body in a first step, themagnet body is covered with a protective layer on its outer surfacewhere heavy RE properties are undesired whereas areas with heavy REproperties are desired are not covered with the protective layer on theperiphery, i.e. the outer surface of the magnet body on a second step.In a third step, heavy RE materials are deposited on the surface of themagnet body that is not covered by the protective layer e.g. via vaporcontaining Dysprosium. The magnet is then annealed at highertemperatures to enable diffusion of heavy RE along the grain boundariesinside the magnet body. Diffused Dy replaces the Nd in NdFeB grains andthe expelled Nd atoms form a continuous layer around the newly formed(Nd, Dy)FeB grains. Such layers also magnetically isolate the grain formthe neighboring grains. By this procedure inside the magnetic body afirst region having different magnetic properties compared to the secondregion, i.e. the region proximate to the outer surface/periphery of themagnet body. This process ultimately leads to the improvement of thecoercivity for more than 50% without changing the remanence compared toa magnet body produced according to the first step only.

A first problem of that method resides in that the second region canonly be at the surface of the body. A second problem of that methodresides in that only second regions having a thin overall thickness canbe realized. As a result, the design freedom of the second region of themagnet is very limited.

Another approach resides in employing an additive manufacturing method.Additive manufacturing is an emerging technology, which allows themanufacture of complex shaped parts in a layer-wise building processdirectly from CAD design data. This makes it an attractive manufacturingmethod especially for complex shapes in a very short time period fromthe design to the final component. For metals, the building ofcomponents can be achieved in a powder bed by employing either a laserbeam (SLM: Selective Laser Melting) or an electron beam (EBM: ElectronBeam Melting). The method received much attention recently. However, atthe moment there are only a limited number of materials (in totalroughly below 20 different materials) available and known, which can beproduced by this method.

A substantial limitation of today's SLM and EBM methods for metalsresides in that the chemical alloy composition and the materialmicrostructure cannot be varied and controlled locally (in small volumeelements at the microstructural level). Therefore, it is not possible tobuild 3D designed, multicomponent microstructures during the buildingprocess of the 3D component.

Another approach for producing a permanent magnet is disclosed inWO2013/185967A1. The method according to this approach uses a focusedenergy beam (laser beam or electron beam) for the selective sintering ofpowders. The main target of the process is to conserve both the originalmicrostructure and the morphology (shape) of the powder particles of thefeedstock. This is achieved by selecting in the sintering process atemperature-time combination, which only leads to the formation ofsintering necks between powder particles, thus avoiding microstructuralchanges (e.g. grain growth, recrystallization) within the particles, andavoiding a change of the morphology of the particles. This means, thatthe method is naturally limited to a early stage of sintering, whereonly sintering necks are formed. In this early stage of sintering,substantial densification of the powder by volume shrinkage and porefilling does not occur. Therefore, the described method always leads toa high amount of residual porosity in the final microstructure. Typicalvalues are above 30 to 40 vol. % of porosity.

A major disadvantage of this method resides in that undesired changes inthe crystal microstructure and morphology of the particles can only beachieved by the cost of a high residual porosity, for example a magneticporosity of 30 vol. %. In an embodiment of WO2013/185967A1, a furthernon-metallic material such as glass or a polymer is added at a fractionbelow 10 wt. % (weight percent) such that the spherical morphology andmicrostructure of the magnetic particles remains conserved. That methodleads to microstructures and properties, which are similar andcomparable to polymeric bonded magnets. In addition the method has thedisadvantage of generating a material with very low mechanical strengthand toughness, due to the high porosity. In addition, as the particlesare connected by sintering necks in a three dimensional network, eddycurrents cannot be efficiently reduced, because of high conductivitiesin the sintering necks. Therefore, the porosity does not improvesignificantly eddy current losses. Compared to conventionally sintered,dense magnets, the energy density (BH)max and the mechanical performanceof magnets obtained by WO2013/185967A1 is low. Thus, magnets ofWO2013/185967A1 need more volume for the same performance compared withconventionally sintered, dense magnets. This is a substantial drawbackfor all kinds of applications (especially for electrical machines),where compact designs with high energy densities are preferred.

Polymer bonded RE magnets consist of magnetic particles (based on REpermanent magnets) in a polymer matrix. With polymer bonded RE magnetsthe limitation of very simple magnet geometries can be partly overcome,as e.g. injection molding or other polymer shaping methods can beapplied. However, these magnets have the drawback of substantially lowermagnetic performance (lower energy density, lower polarization, lowercoercivity), as those magnets contain a high amount of polymer(typically far above 30 vol. %). Furthermore, the mechanical properties(strength, creep), and maximum operation temperature are substantiallylower compared to sintered RE permanent magnets.

Soft magnetic materials play a key-role for electrical applications intransformers, motors, and generators. Various material grades indifferent alloy compositions are available, like polycrystalline (e.g.Fe, Fe—Si, Ni—Fe, Co—Fe base), amorphous (e.g. Fe—B—Si, Fe—Ni—B—Si,Fe—Si—B—P—Nb), and nanocrystalline (e.g. Fe—Cu—Nb—Si—B) materials. Dueto their moderate cost, crystalline Fe—Si based electric sheets (withtyp. 3% Si) are widely used in both non-oriented and grain-orientedgrades. In order to reduce eddy current losses magnetic cores areusually built up of a laminated stack of many thin sheets (typical.sheet thickness 0.3-0.5 mm). Sheets are produced by elaborate hot andcold rolling mill technology combined with heat treatment steps. Thesheets are stamped to the desired dimension and electrically isolated byapplying a ceramic or polymer layer between the sheets. The laminatedstack has to be mechanically clamped or bonded by an adhesive in auseful way. The whole process of building a laminated core from thinsheets is elaborate, time-consuming and costly. In addition, thestamping process or any deformation of the electric sheets degrades themagnetic properties. Therefore, additional annealing treatments have tobe performed to partly recover the initial properties by a release ofgenerated internal stresses. It is known, that core losses can bereduced in general by reducing the thickness of the sheets to a minimumof typ. 0.1 mm. However, this has the drawback of additional cost andcomplexity in the manufacture of a laminated magnetic core. Rapidlysolidified amorphous and nanocrystalline SM materials offer the lowestcore losses and provide the highest energy efficiency. A main drawbackof these materials is their high material and production cost. In orderto achieve an amorphous or nanocrystalline state, the molten material israpidly solidified from the liquid state at very high cooling rates(typically 104-106 K/s). This can be achieved only by casting very thinribbons (typ. 20-50 μm) on a rotating copper wheel. As a drawback it iselaborate and costly to produce magnetic cores based on this very thinribbons. Another drawback of amorphous and nanocrystalline soft magnetmaterials resides in their typically high susceptibility to corrosion.To protect the ribbons from corrosion and to lower eddy current losses,ceramic or polymeric coatings of the individual ribbons have to beapplied.

Summing up, a fundamental drawback of today's soft magnet coretechnology is the elaborate and costly manufacturing process, which is aconsequence of the layered sheet material concept. Moreover, onlycomparatively simple/basic core geometries can be manufactured, whichlimits the degree of freedom in design of advanced, more energyefficient electrical devices drastically.

GENERAL DISCLOSURE OF THE INVENTION

An object of the present invention resides in providing a magnet thatallows for more design freedom of the first region and the second regionand for realizing more complex geometries of the magnet body than forconventional magnets.

This object is achieved by a magnet according to the following basicembodiment having a magnet body that comprises a first region with firstmagnetic properties. A second region with second magnetic propertiesthat are different to the first properties. The location of the firstregion and the second region within the magnet body is freelypredeterminable.

Owing to the new method the magnet is produced, the design freedom ofthe magnet body is increased tremendously. Compared to known magnetmanufacturing methods it becomes possible to allocate the second regionjust there where it is actually needed once built in an electricaldevice, such as a motor for example. Depending on the size and shape ofthe second region compared to the first region, it becomes possible toreduce the RE content of rare earth elements in the magnet bodydrastically such that the overall cost of the magnet body can bedrastically lowered. Also spacially more extended second regions thanfor the known magnet bodies can be realized with essentially no extraeffort. A second advantage resides in that the overall magneticperformance (efficiency) of a magnet body according to the presentapplication can be way higher than a conventionally produced magnet bodyhaving the same outer dimensions as will be explained by way of anexample. During transient conditions, field pulses tend to reduce theflux in magnet to negative values relative to magnetization direction.The eddy currents flowing in the distal ends, i.e. the end regions of amagnet body having an elongated shape protect a central region inbetween the end portions from that pulse. The downside of such aprotection resides in that the distal ends of the magnet body aresacrificed in that they will be demagnetized after a certain amount oftime in use of the electric device such that they cannot contribute tothe overall magnetic performance any longer. In conventional electricaldevices that inevitably led to the consequence that the magnet body hadto be designed larger than actually required in order to ensure asatisfactory long-lasting use of the electric device. Entirely differentthereto allows the new magnet to allocate the second region in the areaof the distal ends and the first region in the center area. If thesecond region has a higher coercivity than the first region in thisexample, the distal area does not need to be sacrificed to such a largeextent for ensuring the required minimal magnetic performance also aftera long lifetime of the electric device. As a consequence, it becomespossible to lower the overall dimensions of the magnet body compared tothe aforementioned conventional magnet body or to enhance the overallmagnetic performance if the same outer dimensions of the aforementionedconventional magnet body are available in the electric device. As onecan see, the present magnet body can contribute essentially to aminiaturization of electric devices.

Expressed in more general terms, the first region having at least one ofa coercivity and a remanence value that is different from the value ofthe second region can be designed such that only a minimal RE content isrequired also in high end applications.

For tuning the magnetic performance it has been proved advantageous thatthe first region has a different microstructure than the second region.More precisely, it has been proved that magnets having an average sizeof magnetic grains in the first region which is larger than an averagesize of magnetic grains in the second region are desirable. Notablesatisfactory results in terms of achievable magnetization values havebeen accomplished if the average size of magnetic grains in the firstregion is at least 20% larger than the average size of magnetic grainsin the second region. Since a difference of the average size of magneticgrains in the second region to the first region proved a strong measure,very satisfactory magnets can be realized if the average size ofmagnetic grains in the first region is at least 50% larger than theaverage size of magnetic grains in the second region.

Besides the size of the magnetic grains in the first region and thesecond region it proved that also the overall average shape of themagnetic grains plays a role. Expressed more generically, it isadvantageous in view of the overall magnetic performance if the averageshape of magnetic grains in the first region is different to an averageshape of magnetic grains in the second region. Notable satisfactoryresults in terms of achievable magnetization values have beenaccomplished if the average shape of magnetic grains in the secondregion is at least 30% more elongated with respect to the average shapeof the magnetic grains in the first region. The elongated average shapeof magnetic grains in the second region can also be referred to as ofcolumnar shape of magnetic grains. An alternative description of theterm ‘elongated’ may reside in that the average magnetic grains in thesecond region have a ratio of a longest dimension with respect to itsgravity center to a shortest dimension with respect to the gravitycenter of at least 2:1.

The new manufacturing method also allows to tune the magnet body suchthat the chemical composition of the first region differs from thechemical composition of the second region. That way, it becomes possiblethat the magnetic grains in the first region have a different chemicalcomposition than the magnetic grains in the second region. Depending onthe requirements, the second region is located at the periphery of themagnet body and may comprise a chemical element like Dysprosium thatconfers the second region with better coercivity properties than thefirst region located surrounded by the second region, for example.

Depending on the embodiment the second region can be an edge region or acorner region of the magnet body. Also a combination thereof can berealized. The term ‘corner region’ is understood as an area of themagnet body extending along a border or ridge where several shellsurfaces meet one another. Different thereto, the term ‘edge region’ isunderstood as a region extending over a shell surface of the magnetbody, e.g. over two lateral surfaces that are arranged opposite to oneanother.

The new manufacturing method also provides for an essentially freegrading. Compared to known diffusion techniques where rare earthelements are brought in peripheral regions of the magnet body, itbecomes possible now to design the thickness of the second region waymore freely. Depending on the required magnetic properties of themagnet, a second region depth of the second region extendingperpendicularly to a surface of the at least one of an edge region and acorner region of the magnet body is at least 1 mm, in embodiments atleast 3 mm, and in yet other embodiments at least 8 mm.

As in many cases, it is desirable that the magnet body has particular,i.e. graded magnetic properties only on all of its lateral surfaces butnot on its bottom surface and its top surface. Good results areachievable if the magnet body is substantially of prismatic overallshape having a rectangular cross-section with a body length and a bodywidth when seen from a direction in which a body thickness extends, i.e.the building direction. The second region is substantially tubular andhas a ring-shaped cross-section when seen from the direction in whichthe body thickness extends rectangular cross-section. The termring-shaped shall not be interpreted narrowly such as to encompass onlycircular cross-sections, but broadly to cover also polygonalcross-sections. The outer contour of the ring-shaped cross sectionmatches an outer contour of the rectangular cross-section. A smallestring thickness does not deviate more than 20% to the body thickness ofthe magnet body. The term ‘smallest ring thickness’ is understood as aminimal direction of the ring-shaped second region at its thinnest spot.Examples are not limited to cuboid like geometries, and apply to morecomplex shapes of the magnet body.

Similar to the situation known from transformer applications or thelike, it may be desirable to tune not only the magnetic properties, butalso the insulation properties. This can done in that at least one ofthe first region and the second region comprises an electricallyinsulating layer within at least two neighboring internal layers of thefirst region and/or the second region, respectively. The term ‘layer’ isused as it has a comparatively large surface and a comparatively smallthickness. Depending on the chemical and physical properties of theelectrically insulating layer, it can be employed for tuning of themagnetic path in that it assists the guiding of the flux lines. Anadvantage of such insulation layers resides in that the formation ofeddy currents can be suppressed or at least hampered in an operatingstate of the magnet. Suppressing or at least hampering/limiting theformation eddy currents in an operating state of the magnet isparticularly advantageous in soft magnet applications.

The planar extension as well as the thickness of the insulation layerdepends on the intended application of the magnet.

Depending on the intended properties, the electrically insulation layercomprises an electrically insulating synthetic material, a metal oxide,a metal carbide, a metal nitride, a ceramic, a glass or even a mixturethereof. It is further possible to build a magnet having two differentinsulating layers. Whether these layers are directly applied on top ofone another or whether there are several layers of magnetic grainslocated in between two identical or similar insulation layers depends onthe requirements on the magnet.

Way higher coercivity values than in conventional sintered magnet bodiesare available if the first region or the second region or the firstregion as well as the second region has/have a filling degree ofmagnetic grains per a given volume of at least 85 percent by volume,i.e. at least 85% of the theoretical density per given volume. In yetother words, the voids in the given volume can consume maximally 15% forthe given volume. Superior coercivity and remanence properties areachievable if the filling degree of magnetic grains per a given volumeis of at least 95 percent by volume. Such filling values are way abovefilling values for laser sintered magnet bodies.

All the above advantages are achievable in that the magnet body isproduced by selective laser melting (SLM), by electron beam melting(EBM), by spark plasma sintering (SPS), by laser cladding, by plasmapowder cladding or by thermal spraying. Each of these production methodsleaves specific properties in the magnet body which allows a detectionof the manufactory method once the magnet body is produced.

The above-mentioned production process further allows to form magnets ofalmost any shape. Up to now, the overall shape of the magnetic body waslimited to comparatively primitive and basic geometries. Now, it ispossible to design a magnet such that it has a free-form shape. Examplesof such free-form shapes are arc-shapes, magnets with a mushroom-shapecross section and the like that are different from box-shaped magnetbodies known from the vast majority of electric devices known to theapplicant at the time of filing this application.

Expressed in other words, the above manufacturing methods enable fullflexibility of contour, shape and size design. Although some methodslike SPS may have more restrictions, complex shapes such as geometrieswith one axial direction as needed in motors are perfectly feasible.

The above manufacturing methods also allow for realizing sandwichedlayer sequences that could not been realized with conventionalmanufacturing methods at all, especially not in an economic way. In anexemplary embodiment of a magnet body, the first region is formed as afirst block, wherein the second region is formed as a second block, andwherein the second block is attached to the first block. The term‘block’ shall not be understood in a narrow way to encompass onlycuboidal shapes. Each of these blocks comprises a plurality of layers.Moreover, the sequence of blocks is not limited to the vertical (i.e. inthe manufacturing sequence of the 3D building method) or in thehorizontal extending transversally thereto. In addition, also hybridembodiments having horizontally as well as vertically extending layersequences can be realized now.

In case of permanent magnets additional properties are achievable, suchas explained below.

Advantageous magnets are achievable if the first region comprises a hardmagnet on the basis of a member of a first group, the first groupcomprising one of compositions a) to g), whereas said composition

a) contains Aluminum, Nickel and Cobalt (AlNiCo);b) contains Samarium and Cobalt (SmCo);c) contains Samarium and Iron (SmFe);d) contains Samarium, Iron and Nitrogen (SmFeN);e) contains Iron and Nitrogen (FeN);f) contains Manganese, Aluminum and Carbon (MnAlC);g) contains Manganese, Tin and Cobalt (MnSnCo);h) contains Manganese and Bismuth (MnBi);g) contains hard ferrite;h) contains RE, Iron and Boron (REFeB);i) contains RE and Iron and Carbon (REFeC).

Particularly inexpensive magnets are achievable if the member of a firstgroup is composition a) or e) or g).

Hard ferrites like Strontium ferrites [SrFe₁₂O₁₉ (SrO.6Fe₂O₃)] are oftenused in small electric motors, micro-wave devices, recording media,magneto-optic media, telecommunication and electronic industry. Bariumferrites, BaFe₁₂O₁₉ (BaO.6Fe₂O₃) a common material for permanent magnetapplications. Barium ferrites are robust ceramics that are generallystable to moisture and corrosion-resistant. They are used in e.g.loudspeaker magnets and as a medium for magnetic recording, e.g. onmagnetic stripe cards. Cobalt ferrites, CoFe₂O₄ (CoO.Fe₂O₃), are used insome media for magnetic recording.

Where desired, the second region may contain a hard magnet on the basisof a member of a second group, whereas said second group comprises allmembers of the first group that are absent in the first region. In anexemplary embodiment, the first member comprises AlNiCo and the secondmember comprises NdFeB.

In an advantageous embodiment with respect to the overall costs of amagnet, the first region comprises a composition with a first member ofRE, Iron and Boron (REFeB), wherein the first member of RE is one orseveral rare earth element/elements of the Lanthanide series. The firstmember does not contain all elements of the Lanthanide series. Thesecond region comprises a composition with a second member of RE, Ironand Boron (REFeB), wherein the second member of RE comprises at leastone rare earth element of the Lanthanide series that is absent in thefirst member.

Where required, the second region may comprise an additional chemicalelement like Co, Ti, Zr for enhancing corrosion resistance, if thesecond region is encompassing the first region in full, for example.

Since heavy rare earth elements (HRE) provide for even higher coercivityand remanence values than the remaining elements of the Lanthanideseries it is advantageous if the second member of RE comprises at leastone heavy rare earth element (HRE).

Moreover, inexpensive magnets are achievable if the first member of REcomprises Cerium (Ce), Neodymium (Nd) or both Ce and Nd.

As an alternative, the first region of a magnet comprises a hard magneton the basis of a member of the first group formed by the compositioncomprising RE, Iron and Boron (REFeB) while the second region comprisesa hard magnet on the basis of the same member of the first group as thefirst region. In this embodiment, wherein a weight percentage of the REin the second region is at least 20% higher than the weight percentageof the RE in the first region.

Good magnets are achievable if the average magnetic grain size of thesecond region is below 4 micrometers, whereas the average magnetic grainsize of commercial magnetic grains is currently larger than 10micrometers.

Irrespective of the fact that the magnet is of soft magnetic type or ofpermanent magnetic type, its properties can further be graded asfollows.

For soft magnets it is advantageous if the average magnetic grain sizeof the first region is below 20 nm or is above 50 micrometers.

Not only in soft magnet applications, but also in permanent magnetapplications, it can be desirable, if at least one of the first regionand the second region comprises a terminating layer at a periphery ofthe magnet body. That geometrically outermost layer with respect to themagnetic body can be insulating and provide corrosion protection or canbe electrically conductive to provide magnetic screening againstdemagnetization of the second and/or first region via the induced eddycurrents and can also be a corrosion protection layer at the same time.Depending on the requirements, the terminating layer can be electricallyconducting.

As mentioned above, there are embodiments where at least one of thefirst region and the second region comprises an electrically insulatinglayer located in between at least two neighboring internal layers of thefirst region and the second region, respectively. Such an embodiment maybe employed for suppressing or at least hampering/limiting the formationeddy currents in an operating state of the magnet, in particularly insoft magnet applications.

Adding an additional high electrical conductivity layer along theperiphery of the magnet may contribute to reduce losses. A furtheradvantage of such an embodiment may reside in that this layer also beformed along the contour/periphery of magnet such that a further step ofmachining along these edges becomes unnecessary for reaching the finalgeometry of the magnet body.

In an alternative embodiment, the terminating layer or an additionalterminating layer is electrically insulating. Such a terminating layercan be made of a plastic or ceramic material for ensuring a corrosionprotection of the magnet body in that a protective coating is formed. Inyet another alternative the magnetic body may comprise both anelectrically conducting layer for reducing the negative effects of ademagnetizing field to the magnet body as well as a yet furtheradditional terminal layer made forming a plastic or ceramic enclosure ontop for ensuring corrosion protection of the magnet body.

Regardless, whether the magnet is a soft or a permanent magnet, SM or aPM, it is beneficial if the magnet body has a structure that is one of apolycrystalline microstructure, an amorphous microstructure and ananocrystalline microstructure.

The polycrystalline microstructure comprises at least one of Iron (Fe)and an iron alloy comprising at least one of compositions i) to v),whereas composition

i) contains Iron and Silicon (Fe—Si),ii) contains Nickel and Iron (Ni—Fe),iii) contains Cobalt and Iron (Co—Fe),iv) contains Iron and Aluminum (Fe—Al),v) contains Iron, Aluminum and Silicon (Fe—Al—Si);

The amorphous microstructure in turn comprises an iron alloy comprisingat least one of compositions vi) to x), whereas composition

vi) contains Iron, Boron and Silicon (Fe—B—Si),vii) contains Iron, Nickel, Boron and Silicon (Fe—Ni—B—Si),viii) contains Iron, Silicon, Boron, Phosphorus and Niobium(Fe—Si—B—P—Nb),ix) contains a first element combination of any one of the elements of athird group and a fourth group where the third group contains theelements Cobalt, Iron and Nickel and where the fourth group contains theelements Boron, Silicon and Carbonx) contains a second element combination of any one of the elements of afifth group and a sixth group where the fifth group contains theelements Cobalt and Iron and where the sixth group contains the elementsZirconium, Hafnium and Niobium;

Last, the nanocrystalline microstructure comprises an iron alloycontaining Iron, Copper, Niobium and Boron.

In case of soft magnets additional properties are achievable, such asexplained below.

The manufacturing process allows for more advanced soft magnets to bebuilt having a magnet body that has a structure being at least one of apolycrystalline microstructure, an amorphous microstructure and ananocrystalline microstructure.

Owing to the rapid change of the coercivity of many compositions in arange of a grain size of the magnetic grains between about 10 nm andmore than about a 100 μm, it proved advantageous in turns of a highpermeability (i.e. a low coercivity) if an average magnetic grain sizein the first region is either less than 20 nm or more than 50 μm, andwherein the second region has an average magnetic grain size of 100 nmto 1 μm. That holds true at least for compositions with the chemicalelements Fe—Cu—Nb—Si—B; Fe—Nb—Si—B; Fe—Co—Zr; Ni—Fe of 50 wt %; Ni—Fe of80 wt %; and Si—Fe with 6.5 wt %.

Next, there are also applications where both soft magnetic or semi-hardmagnetic as well as permanent magnetic properties are desired. In anexemplary embodiment of such a magnet, the first region has either acoercivity of less than 1 kA/m or a coercivity of more than 1 kA/m butless than 10 kA/m, whereas the second region has a coercivity of morethan 10 kA/m.

Up to now, the only way to produce such hybrid magnets resided in thatthe soft and the hard/permanent magnet had to be produced separately ofone another and then assembled to the desired magnet body in a furtherstep. In contrast thereto provides the new manufacturing methoddisclosed later in this description for an economic way to produce thedesired magnet body in essentially one go.

If an electric device is fitted with any one of the above-mentionedmagnets, the effects and the advantages of the latter will apply for theelectric device as well. In exemplary embodiments, the electric devicemay be an electric motor, a generator, a power transformer, aninstrument transformer, a magnetic actuator, a linear motion device, amagnetically biased inductor device or the like.

In case of the instrument transformer, the ability to reduce magnetlosses allows for an increase linear range of those devices, forexample.

Next, a number of methods for producing the above-mentioned magnets isdisclosed.

In a most basic embodiment of the method of producing a magnet having amagnet body comprising a first region with first magnetic properties anda second region with second magnetic properties that are different tothe first properties, the method comprising the following steps:

-   -   a) forming a first layer belonging to the first region by        depositing a plurality of first powder portions on a first        predetermined area of the magnet to be built each, and by fusing        the plurality of first powder portions to one another such that        magnetic grains are formed;    -   b) forming a second layer belonging to the second region by        depositing a plurality of second powder portions on a second        predetermined area of the magnet to be built each, and by fusing        the plurality of second powder portions to one another such that        magnetic grains are formed;    -   c) forming a third layer belonging to the first region on top of        the first layer in a building direction of the magnet by        depositing a plurality of first powder portions on a third        predetermined area of the magnet to be built each, and by fusing        the plurality of first powder portions to one another such that        magnetic grains are formed;    -   d) forming a forth layer belonging to the second region on top        of the second layer in the building direction of the magnet by        depositing a plurality of second powder portions on a fourth        predetermined area of the magnet to be built each, and by fusing        the plurality of second powder portions to one another such that        magnetic grains are formed;

The term ‘fusing’ shall not encompass a neck sintering only such asknown from conventional laser sintering processes.

Depending on the actually three-dimension building device dedicated forcarrying out the forming of the magnet body as well as on the desiredproperties of the magnet body, a thickness of the first layer, thesecond layer, the third layer and the fourth layer thickness is in therange of 20 to 200 micrometers.

Where required, the first layer and the second layer are arrangedside-by-side with respect to the building direction of the magnet.Alternatively, the first layer and the second layer are on top of oneanother with respect to the building direction of the magnet.

The depositing of the first powder portions and the depositing of thesecond powder portions can be performed economically by way of a powderbed. In case that the forming method is spark plasma sintering (SPS),the term ‘powder bed’ is understood as comprising all kinds of materialdepositions, regardless how this is built up in a die.

An economically feasible production of magnets is achievable if thedepositing of the first powder portions and the depositing of the secondpowder portions is performed by way of a first deposition head of adedicated three-dimension building device. The term ‘3D printer’ isoccasionally used for designating the three-dimension building device.

Good forming results are achievable if the fusing is achieved by localmelting of powder particles of the first powder portions and the secondpowder portions by one of a laser beam, an electron beam, an ion beam, aplasma beam. Again, the term ‘fusing’ shall not encompass a necksintering only such as known from conventional laser sinteringprocesses.

It turned out to be advantageous in some applications, if the powder bedis preheated before fusing the plurality of first powder portions andthe second powder portions. Preheating could be particularly beneficialfor all these methods including SPS and cladding (e.g. laser cladding),because preheating is helpful for controlling the grain size and phaseformation, reduced energy requirement for local fusing as well as forreducing thermomechanical stresses.

In case of SPS, the fusing is achieved by applying a mechanical load onthe first powder portions and the second powder portions and passing ahigh electrical current through the first powder portions and the secondpowder portions. In an exemplary embodiment, a mold may be employed thathas the following features. First, an outer mold that defines theperiphery of the magnet body. Second a parting wall that delimits aradially inner section of the mold cavity from a radially outer sectionof the mold cavity when seen in the building direction such that asub-cavity having a ring-shaped cross-section is created. Thering-shaped cross section does not need to be of circular type. Manypolygonal shapes are conceivable. Third, a first powder portioncomprising NdFeB is filled into the inner section of the cavity withinthe parting wall. Fourth, a second powder portion comprising (Nd,Dy)FeBis filled into the sub-cavity having a ring-shaped cross-section. Fifth,the partition wall is removed. Next, a high electrical current throughthe first powder portions and the second powder portions such that thepowder portions not only fuse into a solid body each but also fuse toone another to a single magnet body.

Alternatively, it is conceivable to build the magnet body in a die layerby layer, e.g. in that a bottom supporting structure of the die ismovable in the building direction.

Where required, the manufacturing method may further comprise a step ofexposing the first powder portions and the second powder portions or thefused first powder portions and the second powder portions to a magneticfield. That external magnetic field can be present before and/or duringand/or after the consolidation to affect the nucleation/orientationprocess of the magnetic grains.

For conferring the magnet with even more advanced magnetic properties,the manufacturing method may further comprise a step of arranging anelectrically insulating layer in a predetermined further area of themagnet to be built

a) in between the first layer and the third layer; orb) in between the second layer and the fourth layer; orc) in between the first layer and the third layer as well as in betweenthe second layer and the fourth layer, ord) in between the first layer and the second layer; ore) in between the third layer and the fourth layer; orf) in any combination of a) to e).

The term ‘insulation layer’ is employed because of the comparativelylarge surface to the thickness ratio of the layer. The layer-wiseformation of the magnet body allows for a tailored tuning of insulationproperties as well as of the magnetic paths in a magnet. These measuresmay be taken for suppressing or at least hampering/limiting theformation eddy currents in an operating state of the magnet, inparticular in a soft magnet application.

In case of electrically insulating layer extending in the direction ofthe building direction, they may be arranged such that they indent withthe neighboring first to fourth layers such that good mechanicalproperties of the magnet body are still achievable.

An efficient and yet quick way of disposing the material forestablishing the electrically insulating layer is achievable if the stepof arranging an electrically insulating layer is performed by way of asecond deposition head of a dedicated three-dimension building device.The material for forming the electrically insulating layer deposited bythe second deposition head can be solid (e.g. a powder), liquid or byvapor deposition, or by ion plating, for example.

In a preferred embodiment of the manufacturing method, at least one ofthe first region and the second region has a filling degree of magneticgrains magnetic grains per a given volume of at least 95 percent byvolume. That way, magnets having particular strong magnetic propertiesare achievable.

If required, the manufacturing method may have an additional step ofarranging at least one terminating layer at a periphery of at least oneof the first region and the second region.

Depending on the intended purpose and on other conditions likeinterfering magnetic fields in an operating state of the magnet oncebuilt in an electric device, the terminating layer is electricallyconducting or electrically insulating. Moreover, it is possible to applyan electrically conducting layer first and an electrically insulatinglayer, e.g. for corrosion protection, on top of the electricallyconducting layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The description makes reference to the annexed drawings, which areschematically showing in

FIG. 1 a general display of the method for producing a basic firstembodiment of a magnet according to the present invention;

FIG. 2 a microscopic display of a method for producing the magnet ofFIG. 1 showing the forming of magnetic grains;

FIG. 3 a microscopic display of the method for producing a secondembodiment of a magnet according to the present invention. In thismethod, magnetic grains are formed that are chemically different to theremaining magnetic grains, e.g. by way of doping and alloying;

FIG. 4 a microscopic display of the method for producing a thirdembodiment of a magnet according to the present invention. In thismethod, a local deposition of various materials is performed for forminga thin insulation layer in between neighboring layers;

FIG. 5 a morphology and microstructure of a fourth embodiment of amagnet according to the present invention showing a cutout of a layercomprising larger and columnar magnetic grains;

FIG. 6 a general arrangement of a first set-up of a first region and ofa second region in the magnetic body;

FIG. 7 a general arrangement of a second set-up of a first region and ofa second region in the magnetic body;

FIG. 8 a general arrangement of a third set-up of a first region and ofa second region in the magnetic body;

FIG. 9 a general arrangement of a fourth set-up of a first region and ofa second region in the magnetic body;

FIG. 9a a general arrangement of a variation of the fourth set-up of afirst region and of a second region in the magnetic body;

FIG. 10 a general arrangement of a fifth set-up having electricallyinsulating layers in between of magnetic grain areas of the magneticbody in one layer;

FIG. 11 a magnified cut-out through the layer along line A-A of FIG. 10;

FIG. 12 a schematic display of the method for producing a sixthembodiment of a magnet according to the present invention;

FIG. 13 a front view of a circular magnetic core element forming a firstembodiment of an electric device;

FIG. 14 a schematic cross-section through an electric motor forming asecond embodiment of an electric device; and

FIG. 15 a magnified view of area B in FIG. 14 showing a permanent/hardmagnet body.

In the drawings identical items as well as items of identical functionsare given identical reference characters.

WAYS OF WORKING THE INVENTION

In FIG. 1, a magnet 1 having a free-form shaped magnet body 10 ismanufactured by way of applying a plurality of layers 2 layer-wise ontop of another such that the uppermost layer is bonded locally by anenergy beam in a building direction Z to a neighboring, underlying andadjacent layer at least to some extent. A powdery substance 3 is usedfor supporting the magnet body 10 during the manufacturing process. Thepowdery substance is not boded to the magnet 1 during the manufacturingprocess.

The manufacturing process requires a mold structure having a base 4 witha plurality of cooling and heating elements 5 that can be controlledindependently of one another such that a first surface temperature 6 canbe selected instantaneously at the spot in the X-Y direction dependingon the temperature gradient required. A laser beam 7 is turning a layer13 of a first powder composition 8 comprising rare earth elements aswell as Iron and Boron into first magnetic grains 9. For an improvedcontrol of the microstructure during solidification of the melt pool, analloy-specific temperature gradient and cooling rate is applied and keptconstant throughout the whole building process. The temperature gradientis applied predominately in the building direction Z. At solidificationof the melt pool 16, the cooling rate is kept at a constant level duringthe whole building process. Cooling rates are preferably kept at valuestypically above 104-105 K/s. This is achieved by controlling thetemperatures of both the support structure layer 18 and of the toppowder layer of the powder bed 13 in the building chamber. The supportstructure layer 18 is cooled below room temperature or heated above roomtemperature by thermoelectric elements of the cooling/heating element 5or by a suitable liquid medium. The top powder layer 13 is heated aboveroom temperature by optical radiant heaters 19 or any other appropriatemethod. In combination with variation and control of the laser beamparameters (e.g., beam energy, size of focal spot, dwell time, speed inX-Y-direction.

Although in this section examples the use a focused laser as energysource is proposed, an electron beam can be used as an alternative, too.In the case of a laser beam, the process is conducted under aprotective, inert gas atmosphere (such as Argon, for example). In thecase of an electron beam, the process is conducted under vacuum.

RE is Neodymium with about 30 wt %. FIG. 1 reveals along with FIG. 2that the layer thickness of the powder composition 8 of the first powderbed 13 measured in the direction Z and applied by a first depositionhead (not shown in FIGS. 1 and 2, but being similar to a seconddeposition head shown and explained with reference to FIGS. 3 and 4later on) corresponds to a layer thickness 15 of a first layer 2produced by the number of magnetic grains 9 of the same layer, i.e. themagnetic grains having the same height level in the building direction Z(see FIG. 4 for the layer thickness 15).

Although the first powder composition 8 of the first powder bed 13 isshown in FIG. 1 to have a mixture of globular larger powder particleshaving the same diameter like the layer thickness 15 as well as smallerpowder particles having a way smaller size, one has to know that thisdisplay of the first powder composition 8 in FIG. 1 and all subsequentfigures of this application is a simplified one. That simplification isdone for illustrating schematically the fusing process of the magneticgrains 9 and the formation of the layers 2 in melt pool 16 stepwise. Inreality, the first powder composition 8 comprises a plurality of notnecessarily globular powder particles having a powder grain size ofabout 20-150 μm and the powder bed 13 has a lower packaging density thanthe densified layer of magnetic grains 9. Expressed in other terms, theminimum thickness of magnetic grains 9 correlates with the particle sizeof the powder composition 8.

The laser beam 7 emerges from a printing head 12 that is movable atleast in the X-Y-direction and fuses the plurality of first powderportions provided by the first deposition head to one another in the X-Yand Z-direction such that first magnetic grains 9 are formed in a meltpool 16. As evident from FIG. 2 the first magnetic grains 9 grains aredesignated to have a magnetization direction that corresponds preferablyto a magnetic orientation displayed by double-headed arrows 17 in eachof the first magnetic grains 9.

Returning to FIG. 1, the mold structure further has a support structurelayer 18 provided in between the base 4 and the magnet body 10 onceproduced.

Moreover, heating elements such as optical radiant heaters 19 areprovided for preheating the powder bed 13 before fusing the plurality offirst powder portions together by the laser 7.

FIG. 2 further reveals a heat flow 20 displayed as a hatched arrowextending from the melt pool 16 towards the base 4. The melt pool 16 hasa cooling rate that is controlled to be constant.

Because a first layer 2 belonging to a first region having firstmagnetic properties owing to the first powder portions as well as asecond layer belonging to a second region having second magneticproperties owing to second powder portions having different magneticproperties than the one of the first region are present (not shown inFIGS. 1 and 2) the magnet body 10 has two different magnetic propertiesprovided within its single contour.

The filling degree of magnetic grains relative to the given volume is 95percent by volume, i.e. 95% of the maximal theoretical density.Materials processed by this exemplary method exhibit such a densemicrostructure, because of the total melting of powder particles andresolidifiation of the melt-pool. Measured densities are well above 95%,most of the time above 98% of the theoretical density. Themicrostructure of processed materials exhibit a very pronounced texturewith grain orientation in the Z-direction. The minimum dimension ofgrain-orientation in z-direction correlates with the dimension of thepowder layer thickness. For achieving very long, oriented grains inZ-direction, the laser beam movement is controlled in such a way, thatthe laser pattern matches exactly with the pattern of underneath layers.

The described, exemplary method of the present disclosure has severaladvantages compared to the state-of-the-art. It allows the production ofmagnets with complex geometries, which cannot be achieved by knownmethods, at much lower manufacturing cost. It consequently enablesimproved designs of electrical devices (e.g., motors, generators,transformers, etc.) with respect of maximum performance and an optimumenergy efficiency. The design of the device can be optimized by usingnumerical software for multiphysics simulation of the involved magnetic,electric, thermal, and mechanical phenomena. The result of such anumerical design study is an optimum shaped magnet. A CAD software modelis made for the optimum magnet shape. The magnet is directly producedfrom the CAD software model by the exemplary method of the presentdisclosure. This has an advantage of a cost effective and fastprocessing of a final magnet component. In case of RE-based permanentmagnet materials, the cost effectiveness is better compared to prior artsolutions because the many powder metallurgy processing steps can beavoided. Materials processed by the exemplary method of the presentdisclosure have a substantially higher chemical purity, as the risk ofoxygen pick-up is greatly reduced by performing one (e.g., only one)processing step under Argon. In the case of soft magnet materials, theelaborate and costly procedure of sheet production and subsequentassembly to a magnet core can be avoided, which leads to substantiallyreduced production time and cost. Further important advantages areachieved with respect to the microstructure and properties of theprocessed magnets. As a consequence of the highly controlled grainorientation, a very favorable anisotropic texture of the magnet materialis achieved. The axis of easy magnetization of the crystals correlateeither with the principle z-direction or with the X-Y direction of thebuilding process. Therefore, the obtained anisotropic texture leads toan improved performance of the magnets.

A further advantage is achieved for precipitation hardenable alloysystems. Due to the controlled cooling rate over the whole buildingvolume, a very homogeneous state of oversaturated mixed crystal isachieved. The foreign atoms are at high concentration and distributedhomogeneously in the host lattice. This is an optimum precondition forconducting an appropriate precipitation heat treatment step after thebuilding process. By this, very tailored and improved magneticproperties are achieved.

The embodiment of the magnet body 21 shown in FIG. 3 differs to thefirst embodiment of the magnet body 10 shown in FIG. 2 in that it doesnot only has first magnetic grains 9 belonging to a first region 23, butalso second magnetic grains 22 having different magnetic properties thanthe first grains 9 present in the very same layer 2 with respect to thebuilding direction Z. The second grains belong to a second region 24 ofthe magnet body 21. The first powder portions of a first powdercomposition 8 forming the powder bed 13 are deposited on top on asolidified previous layer 2 or on the support structure layer by way ofa first deposition head again. The first powder composition 8 comprisesREFeB, wherein RE is Neodymium with about 30 wt % for forming the firstmagnetic grains 9 are chemically the same as those for forming thesecond grains 22.

The difference of magnetic properties is achieved by depositing asuitable amount of a powdery substance 25 formed by Dysprosium, i.e. adopant on top of the powder bed 13 only in that area that is designatedto be turned into the second region 24 once fused by the laser beam 7.The depositing of the powdery substance forming a dopant 25 is performedby way of a second deposition head 26 that is movable at least in theX-Y direction, and by the doping process proceeds in the melting pool16. That way, magnetic grains having 6 wt % Dy are achievable.

The second deposition head 26 is movable in X-Y direction and enables asecondary building job. The operation of the second deposition head 26is coordinated with the laser operation and with the application of newpowder layers (e.g. the primary building job for forming the powder bed13). Software, for example, controls both the primary and secondarybuilding jobs. The second deposition head 26 places locally materialeither on the already solidified, solid layer 2 or on the powder layer13, depending on the requirement and in a another embodiment. In anycase, the deposited material can be placed at any desired area in theX-Y building surface. The resolution of the printing head materialdeposition (e.g. the secondary building job) is at least in the range ofthe powder particle size of the primary building job. In an exemplaryembodiment, the local resolution of the second deposition head materialdeposition is significantly higher than the powder particle size of theprimary building job. The thickness of the deposited material in thesecondary building job can be varied according to the requirement. Formagnetic materials, only comparatively thin layers in the range of 0.1-5μm, for example, can be deposited. The second deposition head can useany known deposition technology. It was found to use, for example, afluid medium in order to deposit the material in form of droplets. Thefluid medium can be, e.g. a colloidal dispersion of solid particles in aliquid medium, an inorganic precursor, a sol, an ink or the like. In thecase of using a dispersion, the particle size is typically in the rangeof 1 μm or below.

In an exemplary embodiment, the temperature of the support structurelayer (top layer of primary building job) is kept at an elevatedtemperature to ensure a very quick removal of the dispersion medium.This is achieved by, for example, by the optical radiant heaters 19,which are controlling the surface temperature 6.

The deposition head can deposit at least one kind of material. However,if it seems beneficial for achieving the desired properties of thefinally built object, the deposition head can deposit differentmaterials during the secondary building step. This has the advantage,that different materials can be introduced locally into themicrostructure of the primary building step. The method of the presentdisclosure opens up a very high degree of freedom in the 3D design andbuilding of microstructures of multi-component materials. By this it ispossible to tune locally the functional properties of the desired objectat the microstructural level directly from the CAD model of the object.In a further exemplary embodiment, alloying elements can be introduced,which react to new phases with the particles of the primary building jobduring laser melting and resolidification, or the alloying element candiffuse and segregate at grain boundaries. The laser energy and focalspot size is adjusted in order to build either dense layers, which havebeen deposited on solid substrate surface areas, or to form new alloyphases, which result from the deposition of material at powdersubstrate. In general, all metallurgical concepts can be applied locallyat a microstructural level. Especially melt formation (when the meltpool is created by the focused laser beam), controlled rapidsolidification (when the laser is moved to another spot), and thepossibility of heat treatment after the building process have to beconsidered in order to take full advantage of the exemplary method ofthe present disclosure.

By this, functional properties like e.g. electrical conductivity,thermal conductivity, hardness, strength, corrosion resistance,refractive index, magnetic saturation polarization, magnetic coercivity,Curie temperature, and many more can be tuned locally at amicrostructural level directly from a CAD model of the desired object.

For the example of magnetic materials, the secondary building job isused to introduce alloying or doping elements at places in the volume ofthe magnet, where they are needed. In an exemplary embodiment, a heavyrare earth metal (e.g. Dy) is introduced at locations only, where highdemagnetization fields are present. This has the advantage of minimizingthe total amount of Dy needed. Magnets produced by this way aresubstantially cheaper, because of the significantly lower amount of Dyconsumed for achieving the same performance and temperature stability inthe final application of the magnet. Other alloying elements can beintroduced to locally improve the mechanical strength, toughness, andcorrosion resistance in areas where needed for the final application.

The further embodiment of a magnet body 27 shown in FIG. 4 differs tothe first embodiment 10 shown in FIG. 2 in that there is a firstelectrically insulating layer 28, a second electrically insulating layer29 and a third electrically insulating layer 30 provided in betweensubsequent layers and on top of the top layer of magnetic grainsproduced last when seen in the building direction Z.

The material required for building the insulation layers 28, 29, 30 isdeposited on top of first magnetic grains 9 by way of a furtherdeposition head 31 that dispenses a portion of liquid polysilazanepolymer on top of the first grains 9, once they are solidified, in orderto form a precursor of a ceramic. After cross-linking of the liquidpolysilazane polymer, it is decomposed and the polysilazane is turnedinto a ceramic layer with known means. Depending on the requirements,the layer thickness 32 of the first electrically insulating layer 28, asecond electrically insulating layer 29 and a third electricallyinsulating layer 30 is in a range of 0.1 μm up to about 1 μm.

Expressed in more general terms that are not limited to the embodimentshown in FIG. 3, it can be very advantageous for magnetic materials tointroduce thin layers (typically 0.1-5 μm) of an electrically isolatingmaterial, preferably a ceramic (e.g., oxide, nitride, carbide, etc.). Bythis, eddy current losses can be effectively avoided and the efficiencyof the electric device is significantly improved. In volume areas, wherea high concentration of induced eddy currents would be present, thedensity of isolating layers is increased by introducing more layers inthe same local volume zone. By this, eddy currents are very effectivelysuppressed at volume zones where needed only. In consequence, a minimumof non-magnetic material is introduced, which maximizes the volume ofactive magnetic material in the total volume of the magnet. This is animportant advantage for both soft and hard magnetic materials. In thecase of soft magnetic materials, the present disclosure enables thedirect production of magnetic cores with functionally graded layerarchitecture. It is a much faster, less elaborate, and cheaper techniquecompared to the state of the art. Finally, the present disclosureenables higher efficiency of devices, improved magnetic performance,reduced production cost, and the like.

Next let us revert to the morphology and microstructure of a fourthembodiment of a magnet according to the present invention shown in FIG.5. The soft magnet shown in FIG. 5 shows a close up of a single layer 2formed in the building direction Z having a thickness of about a 100 μm.In this embodiment of a manufacturing method, the first powdercomposition was used both for forming the first magnetic grains 9 aswell as the second magnetic grains 22.

On the left side of FIG. 5 one can see that the first magnetic grains 9are mostly larger and columnar in the first region 23 whereas they aremostly cuboid with a quite quadratic cross-section in the X-Z directionin the second region 24. In this embodiment of a manufacturing method,the different grain sizes and orientations of the magnetic grains havebeen caused by different printing parameters applied to the differentregions 23, 24. The columnar first magnetic grains 9 contribute to lowercoercivity and thus to a higher permeability, while the smaller grainsin the second region 24 have a lower permeability.

In a variation of this method, the second magnetic grains 22 do not needto be produced by a variation of the printing parameters but by adedicated powder bed based on a second powder composition than the oneused for forming the first magnetic grains 9.

The general arrangement of a first set-up of a first region 23 and of asecond 24 region in the magnetic body 10 shown in FIG. 6 reveals thatthe magnet body 10 is of cuboid overall shape and has two opposinglateral surfaces that form edge regions 33. The second region 24 isarranged along that edge regions 33. When seen in the building directionZ, the second regions 24 have a wedge-shape cross section. The firstregion 23 is located in between the two second regions 24. The magneticorientation of the grains is again indicated by a double-headed arrow17.

The general arrangement of a second set-up of a first region and of asecond region in the magnetic body 10 shown in FIG. 7 reveals that themagnet body 10 is of cuboid overall shape and has two opposing surfacesthat are delimited in the Y-Z-direction by two corners or edges 34,each. Compared to the embodiment shown in FIG. 6, the second regions 24of this embodiment extend only along these corners or edges 34 and notover the whole end regions 33.

The general arrangement of a third set-up of a first region and of asecond region in the magnetic body 10 shown in FIG. 8 reveals that themagnet body 10 is of cuboid overall shape. In this embodiment, themagnet body 10 has a sandwich construction where a block forming thefirst region 23 is arranged in between two neighboring blocks formingthe second regions 24 when seen in the building direction Z. Each ofthose blocks comprises a plurality of layers 2.

The general arrangement of a fourth set-up of a first region and of asecond region in the magnetic body 10 shown in FIG. 9 reveals that themagnet body 10 is of cuboid overall shape. In this embodiment, themagnet body 10 has a more complex design where a cuboid-shaped firstregion 23 having smaller outer dimensions than the magnet body 10 islocated entirely within the second region 24. Expressed in other terms,the first region 23 is located entirely in the interior of the magnetbody 10 while the whole periphery of the magnet body 10 is formed by thesecond region 24.

A variation of the magnet body according to FIG. 9 is shown andexplained with respect to FIG. 9a . The first region 23 is extended inthe building direction Z such that it hits a bottom surface 35 and a topsurface 36 of the magnet body.

Again, the magnet body 10 is substantially of prismatic overall shapehaving a rectangular cross-section (in the X-Y-plane) with a body length53 and a body width 54 when seen from a building direction Z in which abody thickness 55 extends. The second region 24 is substantially tubularhaving a ring-shaped cross-section when seen from the direction in whichthe body thickness 55 extends, wherein an outer contour of thering-shaped cross section matches an outer contour of the rectangularcross-section (both extending in the X-Y-direction). The smallest ringthickness 56 does not deviate more than 20% to the body thickness 55 ofthe magnet body 10.

Next, a general arrangement of a fifth set-up of a magnet body 10 havingseveral electrically insulating layers in between of laterallyneighboring magnetic grain areas is explained along with FIG. 10 andFIG. 11. The slice of a magnet body 10 shown in FIG. 10 shows a portionof a single layer 2. The magnet body 10 has a plurality of electricallyof internal electrically insulating layers 37 extending in the directionof the building direction Z and in the X-direction or in theY-direction.

Although it is possible that the magnetic body 10 has not only firstmagnetic grains 9 but also different, second magnetic grains as well,the aspect of the vertical insulating layers 37 will be explained by anembodiment having only first magnetic grains for simplicity.

The close-up shown in FIG. 11 through the layer along line A-A of FIG.10 displays that a vertically extending electrically insulating layers37 is provided in between two neighboring second regions 24 having firstmagnetic grains 9, each. The first powder composition for forming thefirst magnetic grains comprises REFeB, RE is Neodymium with about 30 wt%. As to the particle size see FIG. 2.

The third grains 38 of the electrically insulating layer 37 are formedof the very same first powder composition as the first grains 9 but theyare heavily doped with Iron (e.g. 10 wt % iron) deposited on the powderbed before the fusing process with the laser beam 7 similar to what isdisclosed in FIG. 3. As a result of this treatment, the electric and themagnetic properties of the third grains 38 have been destroyed or atleast heavily lowered compared to the first magnetic grains 9 such thatthe desired electrically insulating effect in the X-Z and in the Y-Zdirection is achieved.

However, the mechanical rigidity of the magnet body in the area of theelectrically insulating layer 37 is not affected excessively, becausethere is still a metallic bonding of the third grains 38 to the firstgrains 9 in the lateral directions X and Y.

The magnetization direction and the direction of flux perturbation isextending in the building direction Z.

Next, a schematic display of the method for producing a sixth embodimentof a magnet according to the present invention is explained with respectto FIG. 12. Contrary to the embodiment explained in FIG. 1 and FIG. 2,this method employs a building structure that is not based on a commonCartesian coordinate system having X-Y- and Z-directions but on adrum-like, or more arbitrary building structure having a curved shellsurface which rotates stepwise about an axis (not shown) in a directionW. Nonetheless, the building direction Z as well as the grainorientation 17 having a microstructural texture extends bottom-up, i.e.from a radially inner area to a radially outer area.

The layer 2 is presently created on top of a substrate 40 (that mightwell be formed by an earlier produced layer 2 having identic magneticgrains 9 as the radially outer layer 2). In this production method, alsoreferred to as laser cladding, laser metal deposition or blow powdertechnology, the powder bed is not deposited on the solidified lowerlayer 2 or the substrate 40 (for example formed in an embodiment by alaminated core) well ahead of the actual fusion in a melt pool 16 causedby laser beam 7, but step-wise by a carrier gas transporting the firstpowder composition 8 to the melt pool 16. The deposition of the firstpowder composition 8 as well as of the energy source for the laser beam7 is done by a combined printing head 41. The combined printing head hasa printing head 12 and an annular hollow nozzle 42 led around theprinting head 12 such as to form a funnel. The solidified magneticgrains have a microstructured texture extending in the Z-direction. Asuitable gas stream 43 of Argon, for example, comprising a predefinedamount of the first powder composition 8 as the one mentioned in thecontext of FIG. 2 is directed coaxially to the laser beam 7 through thenozzle 42 to the melting pool 16 or to the place of the melting pool tobe formed next.

As an option of this manufacturing method, an electric coil 44 may bearranged at an end of the nozzle 42 for exposing the first powdercomposition 8 to an external magnetic field such that a particle andcrystal orientation during the deposition is achievable. This measure isnot limited to this embodiment and is applicable to more complexsurfaces and deposition structures.

Next, a first embodiment of an electric device 45 is shown and explainedwith reference to FIG. 13. FIG. 13 shows a ring-shaped magnetic coreelement 46 having both first region 23 having soft magnetic propertiesas well as a second region 24 having hard magnetic properties. The newmanufacturing technique allows for producing the magnet body 10 layerwise such that both the soft magnetic first portion and the hardmagnetic body are produced in the substantially same manufacturingprocess. Such a magnet body 10 may be employed in the reactorarrangement for an alternating current such as disclosed in EP2104115A1,for example.

A second embodiment of an electric device 45 is shown and explained withreference to FIG. 14 and FIG. 15. FIG. 14 shows a cross-section througha rotor 47 of an electric motor. The rotor 47 comprises a carriersection 48 with a plurality of slots 49 extending in the direction ofthe rotating axis having soft magnetic properties. Such a rotor designis known from the so-called Synrel or Syn-Reltype. The slots 49 aredesigned to receive permanent magnets 50 having a matchingcross-section. Except in area “B” the permanent magnets 50 have not beenshown in FIG. 14 for ensuring that the parts and geometries can berecognized better. FIG. 14 shall not be as a full example covering alldemands and approaches to material composition along the portions of thegeometry. Variations with multiple layers of magnets, differentorientations and shapes of magnets may also be considered.

FIG. 14 further discloses that the overall soft magnetic carrier section48 has a polycrystalline first region 23 for forming a low coercivityregion in an operating state of the electric motor. Losses as well asconductivity do not matter in this first region 23. The grain size ofthe magnetic grains comprising Iron and Silicone (Fe—Si), or a Fe—Co, orFe—Ni, or similar soft magnetic compositions in this region in the coreof the component, the grain sizes are below about 20 [nm] or above 50[μm]. A lamination with electrically insulating layers (28, 29, 30) suchas explained in the context of the embodiment in FIG. 4 are not needed.

The carrier section 48 further has a peripheral area or rim area 51 withrespect to a rotation axis 52 of the rotor 47. Said rim are 51 issubject to high mechanical stresses as well as high magnetic fluxvariations. The rim area corresponds to relatively low coercivity buthigh permeability region, but is in need of a loss managing featuringlaminated polycrystalline structures or microstructures that arenanocrystalline or amorphous. The laminated polycrystalline structuresare formed as explained in the context of FIG. 4 where the production ofelectrically insulating layers 28, 29, 30 is disclosed. The grain sizeof the magnetic grains in this rim area 51 is below about 20 [nm](nanocrystalline or amorphous) or above 50 [μm] (with lamination).Therefore, the rim area 51 qualifies as a further first region 23 in thecontext of this disclosure. Having the above-mentioned grain structurein the rim area 51 is further advantageous as it contributes to a highmechanical rigidity that is very desired in that comparatively smallzone at the periphery of the magnet body of the rotor 47.

The carrier section 48 further has intermediate areas located in betweenneighboring slots 49 as well as in between peripheral ends of the slots49 and the shell surface of the rotor 47 forming so-called bridges.

A bridge is needed to restrain the permanent magnet 50 and polestructure and secure it to the rotor 47. Thus, for mechanicalconsiderations, the bridge is desired to be as thick as possible. Thedownside is, that a thicker bridge magnetic flux to not cross the airgap of the electric machine and therefore adds to the overall costs ofthe machine since an increased permanent magnet is required forcompensating that disadvantage. It needs to be mentioned that thedemands on the soft magnetic side here are independent of whether thereare hard magnets 50 being placed on the rotor 47 of the machine or not.If hard magnets 50 are used, the bridges would have to be thicker thanin applications where no hard magnets are present. This is because ofthe increased centrifugal forces. However, the overall demands anddesires will remain for soft magnetics.

Now returning to the embodiment of FIG. 14, one portion of thisintermediate area is located at a base of the V-shape formed by theslots 49, which intermediate area is nearest to the rotation axis 52,there is a need of a high coercivity and a low permeability.Accordingly, the grain size of the magnetic grains in this area ischosen to be in a range of about 100 nm to about 1 μm. Therefore, thatintermediate area qualifies perfectly as a second region 24 in thecontext of the present disclosure. As a result, the aforementionedmagnet production methods traverse the present problem that largerSynrel type machines are not feasible because they would require largerpole numbers and thus exceed known structural limitations owing toincreased bridge widths required for sustaining increased centrifugalforces and the resultant reduction of magnetic anisotropy. Contrarythereto, the present method allows for building such larger Synrelmachines now because it forms an opportunity for building sufficientlystrong bridges. Owing to no reduction of the anisotropy or even anincreased anisotropy higher saliency ratios of the electro motor isachievable.

A close up of the hard or permanent magnet 50 in section “B” of FIG. 14is provided in FIG. 15. The elongated cross-section of the permanentmagnet 50 is produced similar to the embodiment of the magnet bodydiscussed with respect to FIG. 8. However, in the present hard magnetembodiment the areas for meeting the high coercivity requirements arelocated at opposite, i.e. distal ends 24 of the magnet body 50 withrespect to a central, i.e. proximal first region 23 having comparativelylow coercivity requirements.

LIST OF REFERENCE CHARACTERS

-   -   1 magnet    -   2 layer    -   3 powdery substance    -   4 base    -   5 cooling/heating element    -   6 first surface temperature    -   7 laser beam    -   8 first powder composition    -   9 first magnetic grains    -   10, 21, 27, 39, 47, 50 magnet body    -   12 printing head    -   13 powder bed/layer of powder composition    -   15 layer thickness    -   16 melt pool    -   17 grain orientation    -   18 support structure layer    -   19 optical radiant heaters    -   20 heat flux    -   22 second magnetic grains    -   23 first region (low coercivity)    -   24 second region (high coercivity)    -   25 powdery substance/ink/dopant    -   26 second deposition head    -   28 first electrically insulating layer    -   29 second electrically insulating layer    -   30 third electrically insulating layer    -   31 further deposition head    -   32 layer thickness of insulating layer    -   33 edge region    -   34 corner region    -   35 bottom surface    -   36 top surface    -   37 electrically insulating layer    -   38 third grains    -   40 substrate    -   41 combined printing head    -   42 nozzle    -   43 gas stream    -   44 electric coil    -   45 electric device    -   46 magnetic core element    -   47 rotor of an electric motor    -   48 carrier section    -   49 slots    -   50 permanent magnet body    -   51 rim area    -   52 rotation axis    -   53 body length    -   54 body width    -   55 body thickness    -   56 smallest ring thickness

1. A magnet including a one-piece magnet body comprising a first regionwith first magnetic properties, a second region with second magneticproperties that are different to the first properties, wherein the firstregion has at least one of a coercivity and a remanence value that isdifferent from the value of the second region, and wherein the locationof the first region and the second region within the magnet body isfreely predeterminable, and wherein the first region has a differentmicrostructure than the second region.
 2. (canceled)
 3. (canceled) 4.The magnet according to claim 1, wherein an average size of magneticgrains in the first region is larger than an average size of magneticgrains in the second region.
 5. (canceled)
 6. The magnet according toclaim 1, wherein the average size of magnetic grains in the first regionis at least 50% larger than the average size of magnetic grains in thesecond region.
 7. (canceled)
 8. (canceled)
 9. The magnet according toclaim 6, wherein the average magnetic grains in the second region have aratio of a longest dimension with respect to its gravity center to ashortest dimension with respect to the gravity center of at least 2:1.10. The magnet according to claim 1, wherein the chemical composition ofthe first region differs from the chemical composition of the secondregion.
 11. (canceled)
 12. (canceled)
 13. The magnet according to claim1, wherein the second region is at least one of an edge region and acorner region of the magnet body, and wherein a region depth of thesecond region extending perpendicularly to a surface of the at least oneof an edge region and a corner region of the magnet body is at least 1mm.
 14. The magnet according to claim 1, wherein the second region is atleast one of an edge region and a corner region of the magnet body, andwherein the magnet body is substantially prismatic overall shape havinga rectangular cross-section with a body length and a body width whenseen from a building direction in which a body thickness extends,wherein the second region is substantially tubular having a ring-shapedcross-section when seen from the direction in which the body thicknessextends, wherein an outer contour of the ring-shaped cross sectionmatches an outer contour of the rectangular cross-section.
 15. Themagnet according to claim 1, wherein at least one of the first regionand the second region comprises an electrically insulating layer withinat least two neighboring internal layers of the first region and/or thesecond region, respectively. 16-18. (canceled)
 19. The magnet accordingto claim 1, wherein the magnet body has properties consistent with beingproduced by selective laser melting, by electron beam melting, by sparkplasma sintering, by laser cladding, by plasma powder cladding orthermal spraying.
 20. (canceled)
 21. (canceled)
 22. The magnet accordingto claim 1, wherein the first region comprises a hard magnet on thebasis of a member of a first group, the first group comprising one ofcompositions a) to k), whereas composition a) contains Aluminum, Nickeland Cobalt; b) contains Samarium and Cobalt; c) contains Samarium andIron; d) contains Samarium, Iron and Nitrogen; e) contains Iron andNitrogen; f) contains Manganese, Aluminum and Carbon; g) containsManganese, Tin and Cobalt; h) contains Manganese and Bismuth; i)contains hard ferrite; j) contains RE, Iron and Boron; k) contains REand Iron and Carbon.
 23. The magnet according to claim 22, wherein thesecond region contains a hard magnet on the basis of a member of asecond group, whereas said second group comprises all members of thefirst group that are absent in the first region.
 24. The magnetaccording to claim 22, wherein the first region comprises a compositionwith a first member of RE, Iron and Boron, wherein the first member ofRE is a rare earth element of the Lanthanide series, and wherein thesecond region comprises a composition with a second member of RE, Ironand Boron, wherein the second member of RE comprises at least one rareearth element of the Lanthanide series that is absent in the firstmember.
 25. (canceled)
 26. The magnet according to claim 24, wherein thefirst member of RE comprises at least one of Cerium and Neodymium. 27.The magnet according to claim 22, wherein the first region comprises ahard magnet on the basis of a member of the first group formed by thecomposition comprising RE, Iron and Boron, and wherein the second regioncomprises a hard magnet on the basis of the same member of the firstgroup as the first region, and wherein a weight percentage of the RE inthe second region is at least 20% higher than the weight percentage ofthe RE in the first region.
 28. The magnet according to claim 22,wherein the average magnetic grain size of the second region is below 4micrometers.
 29. The magnet according to claim 1, wherein the averagemagnetic grain size of the first region is below 20 nanometers or isabove 50 micrometers.
 30. The magnet according to claim 1, wherein atleast one of the first region and the second region comprises aterminating layer at a periphery of the magnet body.
 31. (canceled) 32.The magnet according to claim 30, wherein the terminating layer or anadditional terminating layer is electrically insulating.
 33. (canceled)34. The magnet according to claim 1, wherein the magnet body has astructure being at least one of a polycrystalline microstructure, anamorphous microstructure and a nanocrystalline microstructure. 35.(canceled)
 36. The magnet according to claim 34, wherein the firstregion has either a coercivity of less than 1 kA/m or a coercivity ofmore than 1 kA/m but less than 10 kA/m, and wherein the second regionhas a coercivity of more than 10 kA/m.
 37. An electric device comprisingat least one magnet according to claim
 1. 38. (canceled)
 39. A method ofproducing a one-piece magnet having a magnet body comprising a firstregion with first magnetic properties and a second region with secondmagnetic properties that are different to the first properties, whereinthe first region has at least one of a coercivity and a remanence valuethat is different from the value of the second region, and wherein thefirst region has a different microstructure than the second region, themethod comprising the following steps: a) forming a first layerbelonging to the first region by depositing a plurality of first powderportions on a first predetermined area of the magnet to be built each,and by fusing the plurality of first powder portions to one another suchthat magnetic grains are formed; b) forming a second layer belonging tothe second region by depositing a plurality of second powder portions ona second predetermined area of the magnet to be built each, and byfusing the plurality of second powder portions to one another such thatmagnetic grains are formed; c) forming a third layer belonging to thefirst region on top of the first layer in a building direction of themagnet by depositing a plurality of first powder portions on a thirdpredetermined area of the magnet to be built each, and by fusing theplurality of first powder portions to one another such that magneticgrains are formed; d) forming a fourth layer belonging to the secondregion on top of the second layer in the building direction of themagnet by depositing a plurality of second powder portions on a fourthpredetermined area of the magnet to be built each, and by fusing theplurality of second powder portions to one another such that magneticgrains are formed. 40-46. (canceled)
 47. The method according to claim39, wherein the fusing is achieved by applying a mechanical load on thefirst powder portions and the second powder portions and passing a highelectrical current through the first powder portions and the secondpowder portions.
 48. The method according to claim 39, furthercomprising a step of exposing the first powder portions and the secondpowder portions or the fused first powder portions and the second powderportions to a magnetic field.
 49. The method according to claim 39,further comprising a step of arranging an electrically insulating layerin a predetermined further area of the magnet to be built a) in betweenthe first layer and the third layer; or b) in between the second layerand the fourth layer; or c) in between the first layer and the thirdlayer as well as in between the second layer and the fourth layer; or d)in between the first layer and the second layer; or e) in between thethird layer and the fourth layer; or f) in any combination of a) to e).50-53. (canceled)